Article by: Andrew Gordnier
Article applies to: all BMW models with the M52 and S52 engines.
**DISCLAIMER** This will most likely cause a check engine light and will definitely cause your car to not pass smog. I am not a certified technician, so I probably got a few things wrong… please feel free to correct me and I will update this guide to be as accurate as possible. I also just recently picked up this car and the previous owner kept no service record, so there may be a few extra steps necessary to get to all the stuff I removed. Finally, while the block off plate is not 100% necessary for the car to run, it is a good idea because the engine bay will be significantly hotter and the car will be significantly louder without it.
Necessary materials:
10mm socket (both shallow and deep)
SAP block off plate (can be found on ECS, Turner, etc.)
Vacuum line cap (not sure exactly what size, I just bought a variety pack from O’Reilly)
What does the secondary air pump (SAP) do and why would I want to remove it?
The easiest way to think of it is like a primitive EGR system, basically just rerouting some exhaust gas to the intake manifold. However, the SAP has a solenoid that makes it so there is only vacuum going to the pump in open loop (if you don’t know what that is, it’s basically only active on cold start). A common problem that appears and that can be somewhat tricky to diagnose when the pump goes bad is a whine on cold start that sounds like a bad pulley, even if all the pulleys are good (such as in my case). Removing the SAP fixed this whine for me, but this should not be your first diagnostic route, because as I mentioned earlier the car will not pass smog and may get a CEL. Another reason the SAP is often removed is that the assembly takes up quite a bit of space in the engine bay and removing it allows you to access a good few bolts significantly easier. As far as I’m aware, other than the two things I mentioned at the beginning, there are really no problems associated with removing the pump.
Removing the pump:
Before starting work on the car, allow time for it to cool down if you have not yet done so since you will essentially be working directly on the headers. Your first step will be to locate the SAP in the top right (passenger side on US cars) part of the engine bay. Mine was held on with a bracket that only required removal of three 10mm bolts (the red circles on the right image). The air pump itself was held on to the bracket with another three 10mm bolts on the underside of the bracket (red circles on the left image). Since I do not plan on replacing the SAP, I did not care that the rubber fittings between the bolts and pump would break off, but if you do plan on it, remove these bolts more carefully than I did. There will also be a fairly large diameter hose fixed to the SAP and to the solenoid on the headers, be sure to remove that from the SAP side as well. You will also need to unplug the wire that goes to the SAP, which can be found on the bottom and can be removed by squeezing the sides together.
One very important thing to note, DO NOT remove either of the two things in the picture below. The one on the left is the coil pack harness, and the one on the right is the service port, both of which are very important parts.
Removing the solenoid and vacuum lines:
On your exhaust manifold, you should see a somewhat cylindrical object with a large hose out one side and a vacuum line out the other side. This is also held on by 10mm bolts and there are only two of them. I removed the hose first (use a flat-head for the clamps), then undid the vacuum line, then removed the solenoid. I have included a labeled diagram of the solenoid just in case you are unsure what to remove. You will want to attach the block off plate where this solenoid used to go.
Now we need to take care of the vacuum lines. If you trace the line from the solenoid, you will see that the vacuum line attaches to a small length of metal hard line, which then connects back up to another vacuum line. We need to remove this hard line, which is held on by two 10mm bolts. The first one is decently hard to reach because the coolant expansion tank is pretty in the way, but with a shallow socket and some perseverance, it is doable. The second one you will need to use a long socket and fit your hand between the fan shroud and exhaust manifold. These are the two hardest bolts to access, but I was able to do it without removing any other components. After you remove these bolts, you kind of need to twist and pull the hard line out, but with a little elbow grease it should come right out.
After all that is out of the way, it is pretty easy to see where the vacuum line leads to, but I have included a picture just in case. It should attach just below the intake manifold and once you remove it, all that is needed is a small vacuum cap to seal off the nipple. Start the car and make sure there are no exhaust leaks through the block off plate and no vacuum leaks through the cap and just like that, the SAP is removed and the job is done!
